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Abstract:

A size sorting device for carbon nanotube agglomerate and a method for
separating and collecting dispersed carbon nanotubes using the size
sorting device are provided. The size sorting device and method for
separation and collection may use a magnetic field for separating and
collecting dispersed carbon nanotubes.

Claims:

1. A device for sorting a carbon nanotube agglomerate, comprising: a
vessel; an inlet part placed at an upper portion of the vessel; a first
collection part placed at a lower portion of the vessel facing the inlet
part; a second collection part placed at a lower portion of the vessel
facing the inlet part; and one or more electromagnets placed at an
external wall surface at one side of the vessel.

2. The device of claim 1, wherein the vessel is not affected by a
magnetic field; the inlet part is configured to introduce into the vessel
a mixed solution containing the carbon nanotube agglomerate having a
magnetic particle attached thereto; the first collection part is
configured to collect dispersed carbon nanotubes; and the second
collection part is configured to collect the non-dispersed carbon
nanotube agglomerate, wherein the mixed solution is subjected to a
dispersion process prior to being introduced into the vessel.

3. The device of claim 1, wherein the first collection part is placed to
face the electromagnets.

4. The device of claim 1, wherein the vessel is made of glass, quartz,
metal oxide, ceramic, polymer, polymer complex, carbon material, rock or
a metal-containing material which is not capable of being magnetized in a
magnetic field.

5. The device of claim 1, wherein the one or more electromagnets comprise
two or more electromagnets and a magnetic field is applied alternately to
the vessel by each of the two or more electromagnets.

6. A method for separating and collecting dispersed carbon nanotubes, the
method comprising: attaching a magnetic particle to a carbon nanotube
agglomerate to prepare a mixed solution; introducing the mixed solution
into a vessel using an inlet part of the vessel; and collecting dispersed
carbon nanotubes by a first collection part of the vessel while
collecting a non-dispersed carbon nanotube agglomerate by a second
collection part of the vessel using a magnetic field.

7. The method of claim 6, further comprising: dispersing the carbon
nanotube agglomerate in the mixed solution prior to introducing the mixed
solution into the vessel, wherein the preparing the mixed solution
comprises mixing the carbon nanotube agglomerate having the magnetic
particle attached thereto with a fluid.

8. The method of claim 7, wherein the fluid comprises one or a
combination of water, alcohols, organic solvents, surfactant-containing
aqueous solution, glycerin, and low-viscosity polymer.

11. The method of claim 6, wherein the magnetic particle is included in
an amount ranging from about 0.1 part by weight to about 20 parts by
weight with respect to about 1 part by weight of the carbon nanotube
agglomerate.

12. The method of claim 6, wherein the magnetic field is produced by one
or more electromagnets.

13. The method of claim 12, wherein the one or more electromagnets
comprise two or more electromagnets and the magnetic field is applied
alternately to the vessel by each of the two or more electromagnets.

14. The method of claim 6, further comprising inputting the non-dispersed
carbon nanotube agglomerate back into the vessel for repeating the
dispersion process again.

15. The method of claim 6, wherein the method is performed using the
device of claim 1.

16. A device for separating dispersed carbon nanotubes from a
non-dispersed carbon nanotube agglomerate, comprising: a vessel; a first
outlet of the vessel configured to receive the dispersed carbon
nanotubes; a second outlet of the vessel configured to receive the
non-dispersed carbon nanotube agglomerate; and a magnet.

17. The device of claim 16, wherein the magnet is an electromagnet that
is placed on a side of the vessel.

18. The device of claim 17, wherein the first outlet is positioned
farther from the electromagnet than the second outlet.

19. The device of claim 18, wherein the electromagnet is configured to
attract the non-dispersed carbon nanotube agglomerate to a greater degree
than the dispersed carbon nanotubes.

20. The device of claim 18, wherein the electromagnet is configured to
attract the non-dispersed carbon nanotube agglomerate and the dispersed
carbon nanotubes based on a quantity of magnetic particles attached to
each of the non-dispersed carbon nanotube agglomerate and the dispersed
carbon nanotubes.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit under 35 USC 119(a) of Korean
Patent Application No. 10-2012-0155238 filed on Dec. 27, 2012, the entire
disclosures of which is incorporated herein by reference for all
purposes.

BACKGROUND

[0002] 1. Field

[0003] The following description relates to a size sorting device for
carbon nanotube agglomerate, and a method for separating and collecting
dispersed carbon nanotubes using the same.

[0004] 2. Description of Related Art

[0005] A carbon nanotube (CNT) is a material composed of carbon atoms
bonded to each other in hexagonal honeycomb patterns, forming a tube
shape as a whole. Additionally, carbon nanotubes feature high anisotropy
and have various structures such as single-walled structures,
multi-walled structures, bundle structures, etc. Carbon nanotubes include
nanomaterials having a diameter on a nanometer scale (1 nm=one billionth
of 1 m), and generally have extraordinary mechanical and electrical
properties, excellent field emission properties, high efficiency
properties like hydrogen storage mediums, among other unique properties.

[0006] Carbon nanotubes may be synthesized by various methods such as
electric discharge, thermal decomposition, laser deposition, plasma
chemical vapor deposition, thermochemical vapor deposition, and
electrolysis. Since most carbon nanotubes exist in bundle forms in the
stage of synthesis, it is important to separate and disperse the carbon
nanotubes one by one in order to utilize the excellent mechanical and
electrical properties of the carbon nanotubes.

[0007] Typically, as a way to disperse carbon nanotubes in a liquid, a
physical dispersion method such as an ultrasonic process is used. Such a
physical dispersion method using an ultrasonic process may include a
method of putting a single-walled carbon nanotube agglomerate in acetone
and dispersing the carbon nanotubes in the acetone using the ultrasonic
process. In addition to performing the ultrasonic process, the method
includes improving hydrophilic properties of carbon nanotubes by adding a
material such as a surfactant to the solvent. For example, Korean Patent
Laid-open Publication No. 2010-0051927 describes a combined pulverization
and dispersion system enabling dispersion of carbon nanotubes. These
carbon nanotube dispersion methods, however, may not only lack dispersion
effects but may also cause damage to the carbon nanotubes.

[0008] Further, conventional techniques of collecting and separating
certain nanotubes by using a magnetic field are not aimed at collecting
carbon nanotubes dispersed from carbon nanotube agglomerates, but are
mainly intended to separate carbon nanotubes free of metal impurities by
using a magnetic field or to selectively separate only semiconducting or
metallic carbon nanotubes that react to a magnetic field.

[0009] In order to manufacture a carbon nanotube complex with vast market
potential, it is required to acquire excellent physical properties or
electrical conductivity with a minimum use of carbon material.
Accordingly, it is important to obtain a high degree of dispersion of
carbon materials. As an example, if ITO (Indium Tin Oxide), most of which
is imported, can be replaced with a carbon nanotube polymer film, it may
be possible to obtain an import-substituting effect amounting to about
1.3 trillion for 5 years. Moreover, such high efficiency carbon nanotube
dispersion techniques may find applications to various fields such as
conductive polymer, conductive e-paint, electromagnetic field absorber,
and products such as a tennis rackets or a racing bicycles, etc., thus
producing higher added value.

SUMMARY

[0010] This Summary is provided to introduce a selection of concepts in a
simplified form that are further described below in the Detailed
Description. This Summary is not intended to identify key features or
essential features of the claimed subject matter, nor is it intended to
be used as an aid in determining the scope of the claimed subject matter.

[0011] In one general aspect, a device for sorting a carbon nanotube
agglomerate includes a vessel; an inlet part placed at an upper portion
of the vessel; a first collection part placed at a lower portion of the
vessel facing the inlet part; a second collection part placed at a lower
portion of the vessel facing the inlet part; and one or more
electromagnets placed at an external wall surface at one side of the
vessel.

[0012] The vessel may not affected by a magnetic field; the inlet part may
be configured to introduce into the vessel a mixed solution containing
the carbon nanotube agglomerate having a magnetic particle attached
thereto; the first collection part may be configured to collect dispersed
carbon nanotubes; and the second collection part may be configured to
collect the non-dispersed carbon nanotube agglomerate, wherein the mixed
solution may be subjected to a dispersion process prior to being
introduced into the vessel.

[0013] The first collection part may be placed to face the electromagnets.

[0014] The vessel may be made of glass, quartz, metal oxide, ceramic,
polymer, polymer complex, carbon material, rock or a metal-containing
material which is not capable of being magnetized in a magnetic field.

[0015] The one or more electromagnets may include two or more
electromagnets and a magnetic field is applied alternately to the vessel
by each of the two or more electromagnets.

[0016] In another general aspect, a method for separating and collecting
dispersed carbon nanotubes includes attaching a magnetic particle to a
carbon nanotube agglomerate to prepare a mixed solution; introducing the
mixed solution into a vessel using an inlet part of the vessel; and
collecting dispersed carbon nanotubes by a first collection part of the
vessel while collecting a non-dispersed carbon nanotube agglomerate by a
second collection part of the vessel using a magnetic field.

[0017] The method may further include dispersing the carbon nanotube
agglomerate in the mixed solution prior to introducing the mixed solution
into the vessel, wherein the preparing the mixed solution comprises
mixing the carbon nanotube agglomerate having the magnetic particle
attached thereto with a fluid.

[0018] The fluid may include one or a combination of water, alcohols,
organic solvents, surfactant-containing aqueous solution, glycerin, and
low-viscosity polymer.

[0019] The magnetic particle may include a transition metal oxide.

[0020] The transition metal oxide may include one or a combination of iron
oxide, cobalt oxide, nickel oxide, chrome oxide, and magnetite.

[0021] The magnetic particle may be included in an amount ranging from
about 0.1 part by weight to about 20 parts by weight with respect to
about 1 part by weight of the carbon nanotube agglomerate.

[0022] The magnetic field may be produced by one or more electromagnets.

[0023] The one or more electromagnets may include two or more
electromagnets and the magnetic field may be applied alternately to the
vessel by each of the two or more electromagnets.

[0024] The method may further include inputting the non-dispersed carbon
nanotube agglomerate back into the vessel for repeating the dispersion
process again.

[0025] The method may be performed using the device of claim 1.

[0026] In another general aspect, a device for separating dispersed carbon
nanotubes from a non-dispersed carbon nanotube agglomerate includes a
vessel; a first outlet of the vessel configured to receive the dispersed
carbon nanotubes; a second outlet of the vessel configured to receive the
non-dispersed carbon nanotube agglomerate; and a magnet.

[0027] The magnet may be an electromagnet that is placed on a side of the
vessel.

[0028] The first outlet may be positioned farther from the electromagnet
than the second outlet.

[0029] The electromagnet may be configured to attract the non-dispersed
carbon nanotube agglomerate to a greater degree than the dispersed carbon
nanotubes.

[0030] The electromagnet may be configured to attract the non-dispersed
carbon nanotube agglomerate and the dispersed carbon nanotubes based on a
quantity of magnetic particles attached to each of the non-dispersed
carbon nanotube agglomerate and the dispersed carbon nanotubes.

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] FIG. 1 is a diagram illustrating an example of a size sorting
device.

[0032] FIG. 2 is a diagram illustrating an example of an actual layout of
the size sorting device.

[0033] Throughout the drawings and the detailed description, unless
otherwise described or provided, the same drawing reference numerals will
be understood to refer to the same elements, features, and structures.
The drawings may not be to scale, and the relative size, proportions, and
depiction of elements in the drawings may be exaggerated for clarity,
illustration, and convenience.

DETAILED DESCRIPTION

[0034] The following detailed description is provided to assist the reader
in gaining a comprehensive understanding of the methods, apparatuses,
and/or systems described herein. However, various changes, modifications,
and equivalents of the systems, apparatuses and/or methods described
herein will be apparent to one of ordinary skill in the art. The
progression of processing steps and/or operations described is an
example; however, the sequence of and/or operations is not limited to
that set forth herein and may be changed as is known in the art, with the
exception of steps and/or operations necessarily occurring in a certain
order. Also, descriptions of functions and constructions that are well
known to one of ordinary skill in the art may be omitted for increased
clarity and conciseness.

[0035] The features described herein may be embodied in different forms,
and are not to be construed as being limited to the examples described
herein. Rather, the examples described herein have been provided so that
this disclosure will be thorough and complete, and will convey the full
scope of the disclosure to one of ordinary skill in the art.

[0036] In one example, a size sorting device for carbon nanotube
agglomerate includes a vessel 100 which is not affected by a magnetic
field. The vessel includes an inlet part 110 placed at an upper portion
and used to introduce a mixed liquid containing the carbon nanotube
agglomerate having a magnetic particle, a first collection part 120
placed at a lower portion of the vessel facing the inlet part and used to
separate dispersed carbon nanotubes and collect the same, a second
collection part 130 placed at a lower portion of the vessel facing the
inlet part and used to collect a non-dispersed carbon nanotube
agglomerate, and two or more electromagnets 210 placed at an external
wall surface at one side of the vessel. The mixed liquid containing the
carbon nanotube agglomerate having the magnetic particle attached thereto
may be subjected to a dispersion process before being introduced into the
vessel 100.

[0037] In an example, the first collection part 120 may be placed to face
the electromagnets 210. FIG. 1 is a diagram illustrating an example of
the size sorting device. Referring to FIG. 1, since dispersed carbon
nanotubes are hardly affected by a magnetic field, they are discharged
out and collected through the first collection part 120 placed to face
the electromagnets. However, this example is not limited thereto.

[0038] After the magnetic particle is attached to the surfaces of the
carbon nanotube agglomerate, the carbon nanotube agglomerate is mixed
with a fluid and subjected to a dispersion process. After the dispersion
process, the mixed liquid containing the carbon nanotube agglomerate
having the magnetic particle attached thereto is put into the size
sorting device. Then, if a magnetic field is applied repeatedly, the
carbon nanotube agglomerate may be crushed into a small agglomerate and
finally dispersed into individual carbon nanotubes. At this time, the
carbon nanotube agglomerate which is yet to be completely dispersed needs
to be returned back into the dispersion process for the application of
the magnetic field, whereas completely dispersed carbon nanotubes need to
be separated from the non-dispersed carbon nanotube agglomerate and
collected. In this example, the non-dispersed carbon nanotube agglomerate
which have a large size and a large amount of magnetic particles attached
thereto are attracted by the magnetic field and guided into a transfer
path, i.e., the second collection part 130.

[0039] The mixed liquid containing the carbon nanotube agglomerate is
moved slowly from an upper end of the vessel to a lower end thereof.
While the mixed liquid is being moved, a magnetic field is applied by the
two or more electromagnets 210 alternately by an electric current applied
from a magnetic field application device which adjusts the strength of
the magnetic field. As a result, a carbon nanotube agglomerate having a
large size and which is yet to be completely dispersed is attracted by
the magnetic field into the second collection part 130 directly
underneath, whereas the dispersed carbon nanotubes are discharged into
the first collection part 120. Accordingly, the non-dispersed carbon
nanotube agglomerates and the dispersed carbon nanotubes can be sorted by
their sizes.

[0040] In an example, the non-dispersed carbon nanotube agglomerate
collected through the second collection part 130 may be supplied into the
inlet part 110 again after being subjected to a dispersion process in
which the non-dispersed carbon nanotube agglomerate is mixed with a
fluid. If a magnetic field is applied by the electromagnets,
non-dispersed carbon nanotube agglomerates in the mixed liquid containing
carbon nanotube agglomerates with magnetic particles attached thereto may
cling to a wall surface of the vessel on the side where the
electromagnets are provided as a result of the attractive force of the
magnetic field. Then, if the magnetic field disappears, the non-dispersed
carbon nanotube agglomerates may fall directly downwards and be
discharged into and collected by the second collection part 130. Then,
the non-dispersed carbon nanotube agglomerate may be returned back into
the inlet part 110 to be subjected to a dispersion process again.

[0041] The vessel 100 may not be particularly limited as long as it is
made of a material which is not affected by a magnetic field. For
example, the vessel 100 may be made of, glass, quartz, metal oxide,
ceramic, polymer, polymer complex, carbon material, rock or
metal-containing material other than materials containing a metal having
strong magnetism in a magnetic field, etc. Nevertheless, the material of
the vessel is not limited thereto.

[0042] Any number of electromagnets 210 may be used; for example, the
number of the electromagnets 210 may be one, two, or more. In an example,
a magnetic field may be applied to the vessel using two or more
electromagnets in an alternative manner. If the two or more
electromagnets are vertically arranged and the magnetic field is applied
from the electromagnets alternately, a carbon nanotube agglomerate yet to
be completely dispersed may cling to the wall surface of the vessel at
one side due to a magnetic field produced by the uppermost electromagnet.
Once this magnetic field disappears, the non-dispersed carbon nanotube
agglomerate may fall directly downwards and sink down thus moving towards
the next electromagnet from which a magnetic field is applied. The
non-dispersed carbon nanotube agglomerate may undergo this process
repeatedly as much as the number of electromagnets which are arranged.
The number and process of using the electromagnet or electromagnets is
not limited thereto.

[0043] In another example, there is provided a method for separating and
collecting dispersed carbon nanotubes by using the size sorting device
for carbon nanotube agglomerate.

[0044] In this example, a method of separation includes attaching magnetic
particles to a carbon nanotube agglomerate by mixing the carbon nanotube
agglomerate having the magnetic particle attached thereto with a fluid in
order to prepare a mixed solution, dispersing the carbon nanotube
agglomerate in the mixed liquid, introducing the mixed liquid, which has
undergone a dispersion process into the vessel by the inlet part of the
size sorting device, and collecting dispersed carbon nanotubes by the
first collection part 120 while collecting non-dispersed carbon nanotube
agglomerate by the second collection part 130. The separation between the
dispersed carbon nanotubes and non-dispersed carbon nanotubes occurs
through size sorting using a magnetic field.

[0045] For example, the fluid may include a member selected from the group
consisting of water, alcohols, organic solvents, surfactant-containing
aqueous solution, glycerin, low-viscosity polymer, and combinations
thereof, but is not limited thereto. The magnetic particle may include a
transition metal oxide, but is not limited thereto. The transition metal
oxide may include a member selected from the group consisting of iron
oxide, cobalt oxide, nickel oxide, chrome oxide, magnetite, and
combinations thereof, but is not limited thereto.

[0046] In the mixed liquid containing the carbon nanotube agglomerate to
which the magnetic particle are bonded, the magnetic particles may be
included in an amount ranging from about 0.1 part by weight to about 20
parts by weight with respect to about 1 part by weight of the carbon
nanotube agglomerate,. By way of example, the amount of the magnetic
particle with respect to about 1 part by weight of the carbon nanotube
agglomerate in the mixed solution of the carbon nanotube agglomerates may
be in the range of from about 0.1 part by weight to about 20 parts by
weight, from about 0.5 part by weight to about 20 parts by weight, from
about 1 part by weight to about 20 parts by weight, from about 2 parts by
weight to about 20 parts by weight, from about 5 parts by weight to about
20 parts by weight, from about 10 parts by weight to about 20 parts by
weight, from about 0.1 part by weight to about 10 parts by weight, from
about 0.1 part by weight to about 5 parts by weight, from about 0.1 part
by weight to about 2 parts by weight, from about 0.1 part by weight to
about 1 part by weight, from about 0.1 part by weight to about 0.5 part
by weight, or from about 2 parts by weight to about 5 parts by weight.
Nevertheless, the ratio of the magnetic particle with respect to the
carbon nanotube is not limited thereto.

[0047] The magnetic field may be produced by two or more electromagnets
and may be applied to the vessel by the two or more electromagnets
alternately. If the two or more electromagnets are vertically arranged
and the magnetic field is applied from the electromagnets alternately, a
carbon nanotube agglomerate yet to be completely dispersed may cling to a
wall surface of the vessel at one side owing to a magnetic field of the
uppermost electromagnet. Once this magnetic field disappears, the
non-dispersed carbon nanotube agglomerate may fall directly downwards and
sink down towards the next electromagnet from which a magnetic field is
applied. The non-dispersed carbon nanotube agglomerate may undergo this
process repeatedly as much as the number of electromagnets that are
arranged, but the separation process is not limited thereto.

[0048] In an example, the dispersed nanotubes may be preferentially
collected. Also, in accordance with an example, the method may further
include inputting the non-dispersed carbon nanotube agglomerate having a
large size back into the dispersion process again.

[0049] In a conventional method using a ball mill, a ultrasonic wave, a
roll mill, or the like, an unnecessary force may applied to dispersed
carbon nanotubes resulting in deterioration of the quality of the carbon
nanotubes. According to various aspects of the method for separating
carbon nanotube, already dispersed carbon nanotubes can be preferentially
collected and the dispersion process can be continuously performed only
on carbon nanotube agglomerate yet to be completely dispersed.

[0050] An example of the present disclosure will be described in further
detail. However, it should be appreciated by those skilled in the art
that the present examples are not limited thereto.

[0051] FIG. 2 is a diagram illustrating an example of an actual layout of
the size sorting device.

[0052] Referring to FIG. 2, the size sorting device as described above was
installed, and an experiment for carbon nanotube dispersion was conducted
as follows. In this example, prior to separating carbon nanotubes,
magnetic particles are attached to carbon nanotubes by using a radical
initiator adhesion method. Magnetite particles in weight percent three
times as high as that of multi-walled carbon nanotubes (MWNTs) were added
to 100 mL of distilled water in which 1.5 g of 4,4'-azobis(4-cyanovaleric
acid) (hereinafter, referred to as "V-501") was dissolved. Then, by
injecting a nitrogen gas at 80° C. for 10 hours, the magnetic
particles are attached to surfaces of the carbon nanotubes. After adding
NMP (N-methyl-2 pyrrolidone) to the carbon nanotube-magnetite complex in
which carbon nanotube agglomerates and the magnetic particles are bonded
at a weight ratio of 1:3, the carbon nanotube-magnetite complex was
subjected to a physical dispersion process. Upon the completion of the
physical dispersion process, the mixed liquid of the carbon
nanotube-magnetite complex was transferred into the size sorting device.
After the mixed liquid was introduced into the size sorting device, by
applying a magnetic field of 1 T to the electromagnets at an interval of
2 seconds for 8 hours, carbon nanotubes were dispersed.

[0053] Through this magnetic field application process, non-dispersed
carbon nanotube agglomerates having large sizes were attracted by a
magnetic attractive force and discharged into the second collection part,
whereas dispersed carbon nanotubes hardly affected by the magnetic field
were discharged into the first collection part. As a result, the
non-dispersed carbon nanotube agglomerates and the dispersed carbon
nanotubes were collected separately.

[0054] In this example, the carbon nanotube agglomerates having large
sizes that have passed through the second collection part were returned
back to the dispersion process and made to pass through the size sorting
device again. This resulted in only dispersed carbon nanotubes being
collected. This example describes passing the separated carbon nanotube
agglomerates through the size sorting device once more; however, it
should be appreciated that the separated agglomerates may be passed
through the size sorting device again any number of times.

[0055] While this disclosure includes specific examples, it will be
apparent to one of ordinary skill in the art that various changes in form
and details may be made in these examples without departing from the
spirit and scope of the claims and their equivalents. The examples
described herein are to be considered in a descriptive sense only, and
not for purposes of limitation. Descriptions of features or aspects in
each example are to be considered as being applicable to similar features
or aspects in other examples. Suitable results may be achieved if the
described techniques are performed in a different order, and/or if
components in a described system, architecture, device, or circuit are
combined in a different manner and/or replaced or supplemented by other
components or their equivalents. Therefore, the scope of the disclosure
is defined not by the detailed description, but by the claims and their
equivalents, and all variations within the scope of the claims and their
equivalents are to be construed as being included in the disclosure.

Patent applications by Research & Business Foundation Sungkyunkwan University